This invention relates to the field of transducers and particularly to very small transducers utilizing piezoelectric elements and screened-on electrodes for solderless contacts.
Piezoelectric elements used in transducers have utilized electrodes which were formed on the surfaces with contact made to the electrodes by soldered connections. In relatively large transducers, this was completely satisfactory but with increased miniaturization as in such devices as personal pagers, a problem arises with soldering which becomes more troublesome as the active element size becomes smaller. The heat of soldering becomes destructive and the unpredictable mass loading effect of the solder becomes intolerable. Soldering of leads also makes repair or replacement of a unit difficult or impossible.
Another type of transducer assembly is disclosed in a U.S. Pat. No. 3,548,116 assigned to the present assignee and shows one or two piezoelectrically active elements attached to a solid metal plate or vane which then forms one contact terminal. Another U.S. patent, U.S. Pat. No. 4,078,160, assigned to the same assignee, replaces the metal vane with a conductive mesh to reduce the mechanical losses inherent in the earlier solid metal vane. The second contact was made via foil rings conductively cemented to the outer faces of the elements with a foil tab to make connection to a terminal on the housing. These devices were each large enough to drive a speaker cone which was slightly truncated and attached to the center of the structure. In a very small device, such as a personal pager, where a single tone or limited number of tones is utilized, such cumbersome devices cannot, of course, be used and the assembly of an intricate device becomes costly if not impossible. The ideal device would be a highly efficient or low loss unit which could be assembled with a minimum of unskilled hand labor.